diff --git a/esphome/components/openthread/openthread.h b/esphome/components/openthread/openthread.h
index 75d8fe11fd..bd10774fcf 100644
--- a/esphome/components/openthread/openthread.h
+++ b/esphome/components/openthread/openthread.h
@@ -11,6 +11,7 @@
 #include <openthread/instance.h>
 #include <openthread/thread.h>
 
+#include <atomic>
 #include <optional>
 #include <vector>
 
@@ -28,6 +29,8 @@ class OpenThreadComponent : public Component {
   float get_setup_priority() const override { return setup_priority::WIFI; }
 
   bool is_connected() const { return this->connected_; }
+  /// Returns true once esp_openthread_init() has completed and the OT lock is usable.
+  bool is_lock_initialized() const { return this->lock_initialized_; }
   network::IPAddresses get_ip_addresses();
   std::optional<otIp6Address> get_omr_address();
   void ot_main();
@@ -51,6 +54,7 @@ class OpenThreadComponent : public Component {
   uint32_t poll_period_{0};
 #endif
   std::optional<int8_t> output_power_{};
+  std::atomic<bool> lock_initialized_{false};
   bool teardown_started_{false};
   bool teardown_complete_{false};
   bool connected_{false};
diff --git a/esphome/components/openthread/openthread_esp.cpp b/esphome/components/openthread/openthread_esp.cpp
index 9cc9223b52..27712bd86a 100644
--- a/esphome/components/openthread/openthread_esp.cpp
+++ b/esphome/components/openthread/openthread_esp.cpp
@@ -8,6 +8,7 @@
 #include "esp_openthread_lock.h"
 
 #include "esp_task_wdt.h"
+#include "esphome/core/hal.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
@@ -81,6 +82,9 @@ void OpenThreadComponent::ot_main() {
   // Initialize the OpenThread stack
   // otLoggingSetLevel(OT_LOG_LEVEL_DEBG);
   ESP_ERROR_CHECK(esp_openthread_init(&config));
+  // Mark lock as initialized so InstanceLock callers know it's safe to acquire.
+  // Must be set after esp_openthread_init() which creates the internal semaphore.
+  this->lock_initialized_ = true;
   // Fetch OT instance once to avoid repeated call into OT stack
   otInstance *instance = esp_openthread_get_instance();
 
@@ -180,7 +184,8 @@ void OpenThreadComponent::ot_main() {
 
   esp_openthread_launch_mainloop();
 
-  // Clean up
+  // Clean up - reset lock flag before deinit destroys the semaphore
+  this->lock_initialized_ = false;
   esp_openthread_deinit();
   esp_openthread_netif_glue_deinit();
   esp_netif_destroy(openthread_netif);
@@ -210,6 +215,9 @@ network::IPAddresses OpenThreadComponent::get_ip_addresses() {
 otInstance *OpenThreadComponent::get_openthread_instance_() { return esp_openthread_get_instance(); }
 
 std::optional<InstanceLock> InstanceLock::try_acquire(int delay) {
+  if (!global_openthread_component->is_lock_initialized()) {
+    return {};
+  }
   if (esp_openthread_lock_acquire(delay)) {
     return InstanceLock();
   }
@@ -217,6 +225,18 @@ std::optional<InstanceLock> InstanceLock::try_acquire(int delay) {
 }
 
 InstanceLock InstanceLock::acquire() {
+  // Wait for the lock to be created by ot_main() before attempting to acquire it.
+  // esp_openthread_lock_acquire() will assert-crash if called before esp_openthread_init().
+  constexpr uint32_t lock_init_timeout_ms = 10000;
+  uint32_t start = millis();
+  while (!global_openthread_component->is_lock_initialized()) {
+    if (millis() - start > lock_init_timeout_ms) {
+      ESP_LOGE(TAG, "OpenThread lock not initialized after %" PRIu32 "ms, aborting", lock_init_timeout_ms);
+      abort();
+    }
+    delay(10);
+    esp_task_wdt_reset();
+  }
   while (!esp_openthread_lock_acquire(100)) {
     esp_task_wdt_reset();
   }